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SmartHSF™ Mobile Modem

Conexant Systems 

SmartHSF Mobile Modem Data Sheet

1.4.2 Digital Isolation Barrier

The OEM-supplied Digital Isolation Barrier (DIB) electrically DC isolates the HSD from the LSD and telephone line. The HSD

is connected to a fixed digital ground and operates with standard CMOS logic levels. The LSD is connected to a floating

ground and can tolerate high voltage input (compatible with telephone line and typical surge requirements).

The DIB transformer couples power and clock from the HSD to the LSD. (See Mobile Product Updates for qualified

transformers.)

The DIB data channel supports bidirectional half-duplex serial transfer of data, control, and status information between the

HSD and the LSD.

1.4.3 CX20463 SmartDAA Line Side Device

The CX20463 SmartDAA Line Side Device (LSD) includes a Line Side DIB Interface (LSDI), a coder/decoder (codec), and a

Telephone Line Interface (TLI).

The LSDI communicates with, and receives power and clock from, the SmartDAA interface in the HSD through the DIB.

LSD power is received from the HSD PWRCLKP and PWRCLKN pins via the DIB through a half-wave rectifying diode and

capacitive power filter circuit connected to the DIB transformer secondary winding. The CLK input is also coupled from the

transformer secondary winding through a capacitor and a resistor in series.

Information is transferred between the LSD and the HSD through the DIB_P and DIB_N pins. These pins connect to the HSD

DIB_DATAP and DIB_DATAN pins, respectively, through the DIB.

The TLI integrates DAA and direct telephone line interface functions and connects directly to the line TIP and RING pins, as

well as to external line protection components.

Direct LSD connection to TIP and RING allows real-time measurement of telephone line parameters, such as the telephone

central office (CO) battery voltage, individual telephone line (copper wire) resistance, and allows dynamic regulation of the off-

hook TIP and RING voltage and total current drawn from the central office (CO). This allows the modem to maintain

compliance with U.S. and worldwide regulations and to actively control the DAA power dissipation.

1.4.4 CX20437 Voice Codec (S Models)

The optional CX20437 Voice Codec (VC), packaged in a 32-pin TQFP, supports voice/full-duplex speakerphone (FDSP)

operation with interfaces to a microphone and speaker and to a telephone handset/headset.

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